Masking problem

Mar 28, 2013 at 10:59 PM
Edited Mar 28, 2013 at 11:01 PM
Hi! I'm having a problem with the Blit method using the Mask BlendMode. I want to cut an irregular shape from a picture by masking it with a transparent image in that shape like this:
myImage.Blit(dest, mask, dest, WriteableBitmapExtensions.BlendMode.Mask);
Unfortunately, the result is not exactly what I expected: what was transparent in the mask is still empty, instead of filled with the content of the myImage.

Have I misunderstood how the mask works? If yes, could you please give me some advice on how to achieve what I want? Thanks a lot!